GEOPHONE AND METHOD OF MANUFACTURING A GEOPHONE

摘要

A vibration transducer such as a geophone, comprising a central pole piece (110) with a magnet (112) and coil (118) concentrically arranged around it. The position of the magnet (112) is fixed relative to the pole piece (110) a nd the coil (118) is movable relative to the magnet (112). A method of manufacturing a vibration transducer is characterised in that a bobbin carrying the coils is formed from a substantially tubular body which is positioned on a mandrel and at least one coil is wound around its outer surface, the mandrel being removed from the bobbin when the coil is complete . Another method is characterised in that the coil is formed separately and th e bobbin is formed from a substantially tubular body which is positioned insid e the coil and expanded to contact the coil when in position.